4 THE EXTINCT BATRACHIA, REPTILIA 



Nervous System. Cerebral hemispheres larger than optic lobes, extending over and con- 

 cealing optic thalami, and with the lateral ventricles on their outer side. 



Fornix and arbor vitro none ; medulla oblongata, abruptly curved ; olfactory lobes terminal 

 pedunculate. 



Circulatory System. Heart with three or four chambers. 



Aorta with two roots, and rarely an additional bow ; no bulbus arteriosus. 



AVES. 



Osseous structure as in Reptilia, except metatarsal and usually metacarpal bones are con- 

 fluent with each other, and with the carpal and second series of tarsal bones ; first series 

 of tarsals continent with tibia. 



■.Pubis turned backwards and more or less confluent with ischium. 



Nervous System. Cerebral hemispheres larger than optic lobes, and concealing optic 

 thalami with the lateral ventricle. 



Fornix and arbor vitas, present; medulla oblongata bent; olfactory lobes inferior sessile. 



Circulatory System. Heart with four chambers. 



Aorta with one root turning to the right, no bows, and no bulbm arteriosus. 



Class I.-B .A. T 1 1 A C HE I A. . 



The vomer is double, and usually bears teeth in this class; the premaxillary is single 

 or double.* Teeth never planted in deep alveoli. 



There arc six orders, as follows: 



TKAGIIYSTOMATA. 



Caudal vertebra' and frontal bones distinct. Inferior pelvic elements not confluent. 

 (). o. maxillaria, prefrontalia, palatum and pterygoidea wanting; nasalia present. 

 Ethmoid, two lateral pieces, each forming part of palate;. 



Mandibk; toothless, condyloid, teeth pleurodont. No "postorbital and supertcmporal 

 bones." First pair ceratohyals distinct. 



* Two premaxillary bones are usually ascribed to the Batraehia, but in many Salamanders they are confluent. 

 Thus while they are double In Balamandra, they are single in Hemisalamandra, Triton and Diemyotylus. In 

 Amblystomidse they are double. Among Plethodontidai, they vary. Of Plethodontine genera Batrachoseps and 

 Stereochila (Cope gen. nov. tor PuudotrHon marginatut Hallow) have them single, and Plethodon double. Of 

 Spelerpine forms, Maneulus (Cope gen. nov. for Balamandra quadridigUala Holbr.) Oedipus and Spelerpes have but 

 one, and Geofriton and G-yrinophilus (Cope gen. nov. for Balamandra salmonea Btorer Pseudotriton salmoneus Bd.) 

 have two premaxillaries. Dcsmognathus and A.mphiuma tare single premaxillaries. 



